Polymers containing acrylonitrile are important commercial polymers for use in fibers for such applications as fabrics, carpets and carbon fibers. High performance acrylic fibers produced from polyacrylonitrile copolymers are used as precursors for carbon fibers. The tensile modulus of the final carbon fiber has a linear relationship with the modulus of the polyacrylonitrile precursor fiber.
Single-wall carbon nanotubes (SWNT), commonly known as “buckytubes,” have exceptional and unique properties, including high tensile strength, high modulus, stiffness, thermal and electrical conductivity. SWNT are fullerenes consisting essentially of sp2-hybridized carbon atoms typically arranged in hexagons and pentagons. Multi-wall carbon nanotubes are nested single-wall carbon cylinders and possess some properties similar to single-wall carbon nanotubes. However, since single-wall carbon nanotubes have fewer defects than multi-wall carbon nanotubes, the single-wall carbon nanotubes are generally stronger and more conductive.
However, the full potential of the properties of single-wall carbon nanotubes have not been fully realized when incorporated in other materials due to the difficulty of dispersing the nanotubes. The problems associated with dispersing single-wall carbon nanotubes are due largely to their insolubility in most common solvents and their propensity to rope together in SWNT bundles and be held tightly together by van der Waals forces. The lack of significant enhancement in mechanical properties in nanotube-polymer composites has been attributed to the weak interface between the nanotubes and the composite matrix. Therefore, methodology is needed to produce nanotube-polymer composites, and, in particular, fibers which capture the exceptional mechanical properties of single-wall carbon nanotubes. Fabrication of high modulus fibers containing single-wall nanotubes remains a major challenge.